1. Field of the Invention
The present invention relates to the method and apparatus for electrically isolating two adjoining railroad rail sections together and, more particularly, to providing joined insulated rails that are machined.
2. Description of Related Art
The rail system, which permits more than one train to travel on one stretch of track of rail, is generally divided into sections or blocks. The purpose of dividing railroad rails of a rail system into sections is to detect the presence of a train on a section of rail at any given time. Each rail section is electrically isolated from all other sections so that a high electrical resistance can be measured over the rail section when no train is present in that section. When a train enters a rail section, the train will short circuit adjacent railroad rails in which the electrical resistance in the rail section drops thereby indicating the presence of a train.
Railroad rails are generally welded to each other or attached to each other by a steel joint. FIG. 1 shows a typical prior art railroad rail 10 that includes a body 12 having a first side 14 and a second side 16 and defines a head section 18, a web section 22 and a base section 26. The head section 18 having a top surface 20 is connected to the web section 22, which is connected to the base 26. The web section 22 defines at least one slot 24 (shown in phantom) for receiving fasteners.
In order to electrically isolate adjacent rail sections of a rail system, high-performance, non-metallic joints or steel joints having electrically insulated material bonded to its surface are typically used in conjunction with electrically-insulating material placed between abutting ends of joined railroad rails.
FIG. 2 shows a prior art rail joint assembly 30 that includes a first railroad rail 32 having an abutting end 33 and a second railroad rail 34 having an abutting end 35. The ends 33, 35 of the respective railroad rails 32, 34 are joined to each other and a rail joint bar 36 is used to hold the two ends 33, 35 in place. A plurality of holes 38 are defined in the rail joint bar 36, where the holes 38 are adapted to receive fasteners, such as a nut and bolt arrangement (not shown), for securing the rail joint bar 36 to the railroad rails 32, 34. Electrically-insulating material 40, such as polyurethane, is sandwiched between the rail ends 33, 35 to insulate the railroad rails 32, 34 from each other. However, over time the rail wheels will cause the rail ends 33, 35 to deform and/or break apart (referred to in the industry as end batter E shown in FIG. 2), thus causing the railroad rails 32, 34 to contact each other and short out.
FIG. 3 shows a prior art rail joint arrangement 42 that addresses the problems of deformation and end batter of adjoining insulated railroad rails. Like reference numerals are used for like parts. The arrangement 42 includes two joined railroad rails 32, 34 that have been machine cut, tapered and trimmed to compliment one another (collectively known in the industry as a “Z Cut”). This arrangement 42 spreads the impact load of the train wheels over a longer area thus increasing the Moment of Inertia at a section where the railroad rails 32, 34 are joined. Although the arrangement 42 has a high Moment of Inertia, which can be defined as the capacity of a cross-section to resist bending, this arrangement 42 utilizes non-standard railroad rails having a double thick web section 22 (not shown), such that non-standard rail joint bars have to be used when attaching the railroad rails 32, 34 to each other. The use of non-standard railroad rails and rail joint bars increases the cost for the arrangement 42. The electrically-insulating material 40 has uniform thickness throughout its length and insulates from the top to the bottom of the adjacent railroad rails 32, 34.
It is, therefore, an object of the present invention to eliminate the above-mentioned deficiencies by providing a high strength lap joint assembly that utilizes standard railroad rails and other off-the-shelf rail products for electrically isolating two adjoining railroad rail end sections to each other. It is a feature of the present invention to eliminate end batter and to provide a lap joint assembly that is substantially as stiff as a solid railroad rail. It is another feature of the present invention to use bonded rail joints and an adhesive such as an epoxy between the adjoining rail end sections thus increasing the longitudinal bond strength of the lap joint assembly.